The present invention relates to a supporting structure for a motor vehicle, in particular a high powered motor vehicle with sporting characteristics provided with integral four wheel drive.
Supporting structures utilised in motor vehicles of this type comprise a frame obtained by rigidly connecting together, normally by means of welding, sheet metal and metal profiles of various form obtained by cutting and drawing operations. The wheels are resiliently connected to this structure by suitable suspension members such as pivoted arms, shock absorbers, coil springs, which are normally pivotally fixed to suitable regions of the structure itself. The engine and the transmission members such as the gear box, the differential units and the torque dividers are also directly connected to the structure itself with the interposition of suitable supports of deformable material.
Supporting structures of the type described have numerous disadvantages.
First of all, the rigidity of this structure, in particular in the regions where the suspension is attached, is not sufficiently high to avoid the occurrence of local deformations which alter the initial geometric conditions of the suspension and therefore detrimentally affect both the road holding and the driving precision. This disadvantage is particularly marked in motor vehicles with sporting characteristics having high powered propulsion and provided with integral four wheel drive.
Moreover, with supporting structures of this type there is only a modest ride comfort because of the vibrations which are transmitted to the passenger compartment by the suspension and by the engine; in fact the rigidity of such suspension must be rather high in order to maintain correct road holding, and the engine, which is normally disposed in the rear-central part of the motor vehicle, transmits significant vibrations to the passenger compartment.
Finally, supporting structures of the type briefly described are constructionally rather complex because of the large number of parts of which they are composed and because of the form which some of these parts have; the cost of this structure is therefore very high both because of the cost of the associated fittings which must be numerous and complex and because of the amortisation costs of these which is consequent on the small number of production units of motor vehicles of this type.